There are three main types of commercialized solar panels: monocrystalline silicon (Si), polycrystalline silicon (Si) and thin film. The two formers are crystalline solar panels. Monocrystalline Si solar panels have the highest efficiency rates since they are made out of the highest-grade silicon. The efficiency rates of monocrystalline Si solar panels are typically 16-22%. Monocrystalline Si solar panels are space-efficient. Since these solar panels yield the highest power outputs, they also require the least amount of space compared to any other types. Monocrystalline Si solar panels produce up to two times the amount of electricity as thin-film solar panels. Monocrystalline Si solar panels live the longest. Most solar panel manufacturers put a 25-year warranty on their monocrystalline Si solar panels.
The process used to make polycrystalline Si is simpler and costs less. The amount of waste silicon is less compared to the manufacturing process for monocrystalline Si wafers. Polycrystalline Si solar panels tend to have slightly lower heat tolerance than monocrystalline Si solar panels. This technically means that they perform slightly worse than monocrystalline Si solar panels in high temperatures. Heat can affect the performance of solar panels and shorten their life spans. However, this effect is minor. The efficiency of polycrystalline Si solar panels is typically 14-18%. Because of lower silicon purity, polycrystalline Si solar panels are not quite as efficient as monocrystalline Si solar panels. Polycrystalline Si panels have a lower space-efficiency. It is generally necessary to cover a larger surface to output the same electrical power as would a solar panel made of monocrystalline Si.
Both the monocrystalline and polycrystalline Si solar panels are constructed as large panels comprising many solar cells made from silicon wafers electrically connected together and sandwiched between a top layer of tempered glass treated with an antireflective coating and a back sheet. The sandwich structure is then surrounded and supported by a frame constructed from extruded aluminum alloy. The standardization of the panel sizes enables a manufacturer to realize increased economies of scale by mass manufacturing panels. The solar panels are manufactured in standard sizes of approximately 165 cm×95 cm×3.5 cm and would typically weigh 15-20 kg each, or 195 cm×95 cm×4 cm and weight 25-30 kg each. The panels which are produced are large, rigid and fragile. As such it would typically require two or more workers to move and install the panels. The conventional manner of mounting these solar panels is to install footings which are bolted to a roof. Bolting to a roof necessitates holes being punched through shingles with the potential for water leakage. Rails are attached to the footings. The solar panels are then fixed to the rails and sit suspended above the surface of the roof resting on the rails. On a sloped roof, rain can flow under the solar panels and off the roof. The solar panels are factory sealed and are impermeable to water. With solar panels suspended above the roof, there is a possibility of the panels lifting during high winds.
Thin film solar cells, also known as thin-film photovoltaic cells (TFPV) typically consist of multiple layers: an antireflective layer, followed by PV materials, then a contact plate and a substrate. Depositing one or several thin layers of photovoltaic material onto a substrate is the basic gist of how thin-film solar cells are manufactured. The different types of thin-film solar cells can be categorized by which photovoltaic material is deposited onto the substrate. Depending on the technology, thin-film module prototypes have reached efficiencies between 7-13% and production modules operate at about 9%. Future module efficiencies are expected to climb close to the about 10-16%. Some TFPV cells are more flexible and easier to handle than crystalline Si panels. High temperatures and shading have less impact on the performance of thin film solar. In situations where space is not an issue, thin-film solar panels can make sense. Thin-film solar panels are in general not very useful for in most residential situations. They require a lot of space. Monocrystalline Si solar panels produce up to two times the amount of electricity as thin-film solar panels for the same amount of space. Low space-efficiency also means that the costs of PV-systems (e.g. support structures and cables) will increase. Thin-film solar panels tend to degrade faster than mono- and polycrystalline solar panels, which is why they typically come with a shorter warranty.
United States Patent publication No. 2008/0190047 A1 (Allen) teaches a solar roofing kit for placing over a section of roof deck to generate electricity. The kit includes at least one panel having a support plate adapted to support the photovoltaic sheet; a rib extending from one edge of the support plate at a distal end; a received flange extending generally perpendicularly from the distal end of the rib over the support plate; and a hem extending from an opposite side of the support plate; where the hem is adapted to engage a receiver flange on another panel when the panel is mounted on the roof adjacent other panels. The rib extends a predetermined distance greater than the thickness of the photovoltaic sheet so that the receiver flange can extend over the photovoltaic material when it is installed on the support plate.
The solar roofing kit taught by Allen is based upon metal roofing technology, and would be easier to install on a roof than the large conventional crystalline Si solar panels which have many solar cells mounted together in a framed panel and the framed panel mounted on rails on a roof. The installed solar roofing kit has a tidy, low profile appearance. It is expected that the cost to manufacture the components taught by Allen would be quite high since they are not common mass produced articles or simple extrusions. Instead, they are formed sheet metal one by one and having a rather complex curvature.
This prior art solar roofing kit is an application for use with thin film solar module sheeting, not with crystalline Si solar cells or panels. This solar roofing kit has a sheet metal support plate adapted to support the photovoltaic sheet. There is a need for an improved solar roofing kit which will facilitate the installation of more energy efficient crystalline Si solar cells or panels.
There is a need for a system of crystalline Si solar panels which are smaller than the conventional framed panels and are easier to install. There is a need for a system of crystalline solar panels which can be installed on smaller, non-standard sized roofs and, if desired, integrated with the installation of standard shingles.
Crystalline solar panels have a sandwiched construction including a layer of tempered glass, which provides the necessary integral support to the solar panels. A sheet metal support plate is not required for using with crystalline Si solar panels. There is a need for a system of a solar roofing kit which does not incorporate a sheet metal support plate, which would be redundant if used with solar panels supported by tempered glass sheets.
There is a need for a solar roofing kit which takes advantage of mass production capabilities currently available for manufacturing the frames for conventional crystalline Si solar panels to cost effectively produce modular frame elements which will serve the dual purpose of framing the solar panels and mounting the solar panels to a roof.
In order to facilitate repair and maintenance of a solar roofing system, there is a need for a solar roofing kit for which it is relatively easy to replace one or more of the individual solar panels from the solar array on the roof. The splice plate in the kits taught by Allen that connects the left and right solar panels makes it be impossible to replace one failed solar panel in the array. Almost all of solar panels on roof would need to be removed if one failed in the first installed row of solar panels closing-in the eaves of roof. In order to avoid a single solar panel being imprisoned, a new kind of central connector is needed to avoid the connection method in prior art for solar panels to slide into and be connected by the splice plate from left and right sides.